Dye transfer color photography

ABSTRACT

Method of making a dye transfer print by directly applying dye to an imaging medium in which a photographic image is defined by selectively softened portions of a supported photosensitive layer comprising a finely divided photoconductor and a binder therefor, and then transferring applied dye therefrom to a receptor surface, without prior removal of said selectively softened portions of said supported layer to create a photographic relief image.

United States Patent [72] Inventor Hans K. Wong Arlington, Mass. [211Appl. No. 712,931 [22] Filed Mar. 14, 1968 [45] Patented Nov. 16, 1971[73] Assignee lick Corporation Lexington, Ma.

[54] DYE TRANSFER COLOR PHOTOGRAPHY 9 Claims, No Drawings [52] US.96/48, 96/28 [51] Int. Pl G03c 5/24 [50] Field olSeai-eh 96/28, 88, 48;101/464 [56] References Cled UNITED STATES PATENTS 2,713,305 7/1955Yutzy etal 96/30 X 2,834,676 5/ 1958 Stanley et al. 96/28 3,146,1048/1964 Yackel eta] 96/33 3,159,485 12/1964 Van Hoot et 211.... 96/33 X2,013,116 9/1935 Troland 101/464 2,381,704 8/1945 Terry 101/464 PrimaryExaminer-Norman G. Torchin Assistant Examiner-John L. GoodrowAnomeys-Horner 0. Blair, Robert L. Nathans and W. Gary Goodson DYETRANSFER COLOR PHOTOGRAPHY BACKGROUND OF THE INVENTION 1 Field of theInvention This invention relates to improved methods for making dyetransfer prints by transfer of dye to a receptor sheet from an imagingmedium of a type suitable for the preparation of photographic reliefimages, and relates in particular to the use of such a medium, in whicha photographic image is defined by selectively softened portions of aphotosensitive layer, for dye transfer prior to removal of selectivelysoftened portions thereof to form a relief image.

2. Description of the Prior Art Commonly owned copending US. Pat.application Ser. No. 713,022, filed Mar. 14, 1968, of Robert H. Spraguefor Direct Positive Photographic Relief Image," filed on even dateherewith, discloses methods for making direct positive photographicrelief images and dye transfer prints therefrom employing an imagingmedium having a supported photosensitive layer comprising a finelydivided photoconductor dispersed in a binder therefor. Exposure of suchan imaging medium to actinic radiation such as visible or ultravioletlight activates the photoconductor, rendering it capable of effectingchemical reactions which are utilized to develop a visible image in themedium. Specifically, the exposed medium is developed with a developingagent comprising reducible metal ions, whereby free metal is depositedin said radiation-exposed portions. The deposited free metal is nextoxidized to metal ions in the presence of a metal ion-activatedsoftening agent for said binder, whereby the binder is softened inradiation-exposed areas. According to the invention disclosed in thiscopending application, softened binder is next removed fromradiationexposed areas to produce a positive relief image definedtherein by removed and unremoved binder portions. A dye suitable for dyetransfer processes is next taken up into unremoved portions of thebinder and then transferred therefrom to a receptor surface, such as amordanted paper or transparent film base.

SUMMARY OF THE INVENTION According to the present invention it has beenfound that photographic imaging media exposed, developed, bleached, andsoftened according to the process of the prior art as described abovecan be used directly to prepare dye transfer prints by directapplication of dye to the photographic imaging medium in which an imageis defined by selectively softened portions of binder, i.e., withoutprior removal of softened binder to form a relief image. It has beenfound that these softened portions of binder do not significantly takeup dye ap plied thereto and do not transfer significant quantities ofdye therefrom to the receptor sheet in the making of a dye transferprint.

The resulting elimination of the step of removing softened portions ofthe binder prior to the first application of dye thereto involves aconsiderable saving of time in the preparation of dye transfer printsand decreases the chance of image damage during this binder removalstep. Also, elimination of the step of removing softened binder portionsin the preparation of a relief image significantly simplifies thestructure of apparatus for performing the steps necessary for preparingdye transfer prints of an image to be copied.

In the process of this invention, softened portions of binder from thephotosensitive layer of the imaging medium are usually transferred toreceptor surfaces by adhesion thereto during the making of the first orthe first few dye transfer prints. Hence, a relief image is soon formedin the photographic imaging medium, which relief image can then be usedin conventional fashion to make further dye transfer prints. The firstdye transfer print made from an imaging medium to which dye has beenapplied according to this invention, i.e., before formation of a truerelief image in the medium, bears both dye transferred from unsoftenedportions of the binder and deposits of softened binder which tend tobecome adhered to the receptor sheet and are in this manner physicallyremoved from the imaging medium. The softened binder transferred to thedye transfer print is substantially uncolored, i.e., the softenedmaterial has not significantly taken up the dye applied to the imagingmedium prior to contact with the transfer sheet. This softened binderadhering to the print can be readily removed by washing of the printwithout harming its quality.

Most of the softened binder from the imaging medium is generallytransferred when the first contact print is made, but small amounts ofsoftened binder may be transferred in the preparation of subsequentprints. Substantially all of the softened binder is removed from theimaging medium after two or three prints have been made. The reliefimage so formed may now be used, as known in the prior art, for thesubsequent manufacture of multiple dye transfer images.

Details of the preparation of imaging media suitable for forming reliefimages and making dye transfer prints therefrom, and comprising softenedbinder portions defining an image therein, are to be found in theaforesaid copending application, incorporated herein by reference. Theimaging media described in this copending application comprise a finelydivided photoconductor suitably dispersed in a binder therefor to form aphotosensitive layer on a support such as paper, metal foil, plastic,glass, or the like. The photoconductors of greatest utility for use insuch imaging media are compounds formed between metals and elements ofGroup VIA of the Periodic Table, for example metal oxides, sulfides,selenides, and tellurides. Preferred materials from the point of view ofcolor, light sensitivity, ease of development and the like are titaniumdioxide and zinc oxide.

A radiation-exposed imaging medium, in which radiation struck areas ofthe photosensitive layer comprise activated photoconductor, is suitablydeveloped by contacting the exposed medium with a developing agentcomprising metal ions which are reduced by the activated photoconductorto form a deposit of free metal. Next, the free metal deposited inradiation-exposed areas in reoxidized (bleached) to form metal ionsdispersed throughout the binder in radiation-struck portions. Thereoxidation is effected in the presence of a metal ion-activatedsoftening agent for said binder so that those portions of the bindersurrounding the metal ions formed in the exposed medium by reoxidationbecome softened.

According to the present invention, the medium comprising selectivelysoftened binder portions may now be treated with a dye of the typeconventionally used in the photographic arts for making dye transferprints. Monochrome prints may be made, or full color dye transfer printsproceeding as described in detail in the copending application mentionedearlier herein.

DESCRIPTION OF PREFERRED EMBODIMENT The methods and materials of thepresent invention are particularly useful in systems employing hardenedgelatin as a binder for a photoconductor in an imaging medium.

In such a preferred embodiment, a photographic imaging medium comprisinga support layer such as of paper having a finely divided photoconductor,such as finely divided titanium dioxide, dispersed throughout a hardenedgelatin layer on said support is exposed to imaging radiation asdescribed. Lightstruclt areas of the imaging medium are then developedby contact of the exposed medium with a developing agent comprising adissolved metal salt, suitably a dissolved silver salt, resulting in thedeposition of metal in the light-struck areas. The image so formed maybe intensified by techniques analogous to physical development. Themetal image, e.g., a silver image, is next bleached (reoxidized) in thepresence of a softening agent for the gelatin, which becomes softened inlight-struck areas and leaves hardened gelatin in unexposed areas.

Development with silver ion is conveniently done by contacting theexposed imaging medium with aqueous silver nitrate to form a metallicsilver image in the medium. This image can be intensified by contactwith a redox system, preferably an organic redox system such ashydroquinone, metol (p-methylamino phenol sulfate) or the like, whichpromotes further deposition of metal where metal is already present. Themetal ion and redox system may be applied separately or in admixture.

Bleaching solutions having a softening effect on hardened gelatin layersare known in the photographic arts and are taught, for example, inGlafkides, Photographic Chemistry," Vol. 2, Fountain Press, London(1960), page 668.

Because the present invention involves processing of a layeredphotographic imaging medium involving selective softening and theultimate removal of portions of a photosensitive binder layer from asupport layer, the medium is conventionally exposed to imaging radiationfrom its light-sensitive side to insure that softening and removal ofthe binder layer will occur in proportion to the amount of radiationreceived thereby, i.e., that a complete removal of the binder layer fromthe support layer will only occur in those portions of the medium inwhich the light intensity is strongest, penetrating to the interfacebetween the binder layer and support layer. As is also known in the artof preparing relief images by radiationinduced sofiening of a binderlayer, a light-attenuating agent is suitably dispersed in the binderlayer of the imaging medium to control the depth of light penetration onexposure. For example, in panchromatic silver halide films used for theproduction of relief images, finely divided carbon is generallydispersed through the imaging medium as a moderator or attenuator.Alternatively, a yellow dye is often dispersed through silver halidelayers for the same reason.

In the present invention, a moderator or attenuator is also suitablyemployed to control the depth of radiation penetration on exposure. Inthe preparation of positive relief images ancillary to producing fullcolor dye transfer prints, the photoconductor in the imaging medium maybe dye sensitized with known dye sensitizers to be receptive to red,green, or blue light, all as taught in said aforesaid copending patentapplication. The dyes used for this sensitization are generally presentin the binder layer in amounts sufficient for the dye to not also as amoderator or attenuator, so that the need for carbon or an additionaldye as a light moderator is obviated.

A better understanding of the present invention and of its manyadvantages will be had by referring to the following specific examples,given by way of illustration.

EXAMPLE 1 Preparation of a Photographic Imaging Medium Adaptable to theManufacture of Direct Positive Photographic Relief Images 50 grams of anaqueous slurry containing 25 percent of finely divided titanium dioxide(about 0.3-0.4 micron) were diluted with 42.6 ml. of distilled water and3.4 ml. of a percent solution of a commercial wetting agent (Tiwet").The resulting mixture was heated to about 100 F. and then combined with100 grams of a 10 percent aqueous solution of gelatin swelled and heatedto 100 F. 2.6 ml. of a 50 percent aqueous solution of glycerin wereadded to the resulting slurry as a humectant and antifoaming agent, and2 ml. of a 4 percent aqueous solution of formaldehyde were added to theslurry as a hardening agent for the gelatin The resulting slurry wasthen uniformly poured onto a fiat piece of subbed triacetate film anddrawn down with a hot wire rod. The resulting hardened gelatin coatingwas dried for minutes at room temperature and for another 20 minutes atabout 50 C. in a circulating hot air oven.

EXAMPLE 2 Dye Sensitization of a Photographic Imaging Medium A sheet ofthe film prepared as in example 1 was dip dyed for 2 minutes in anaqueous solution containing 100 mg. per liter of Z-(p-dimethylaminostyryl)-4-methyl thiazolium methochloride,

which sensitizes the film to green light. The sensitizing dye here usedacts also as a light moderator to control the depth of light penetrationinto the gelatin binder on exposure.

EXAMPLE 3 Exposure and Processing A 5-second exposure to a photographicimage to be copied was made using a watt lightbulb at a distance of 12inches. A green filter was used in view of the dye sensitization of thefilm to green light.

The exposed printing medium was next developed by contacting with 3 Naqueous silver nitrate solution, briefly draining, and the contactingwith an aqueous solution of 2 percent metol and 0.5'percent citric acidfor l0 seconds to intensify the silver image and render it visible. Theprint was fixed in a standard acid hypo fixing bath and washed.

The film containing a silver image was next bleached for 2 minutes witha sottening bleach of a type known in the art, prepared, for example, bycombining one part by volume of a 3 percent aqueous solution of hydrogenperoxide with three parts by volume of an aqueous solution containing 75grams of CuSO '5l-L0, 2 grams of KBr, 25 ml. of concentrated 14,80 andwater to make 1,500 ml. (cf. Glafkides, op. cit., p. 668). The bleachsoftens the gelatin in the silver image areas of the imaging medium butleaves intact those portions of the gelatin binder where no silver ionis present. The gelatin matrix so prepared was merely rinsed in lukewarmor cold water after removal from the softening bath to rinse off anyfilm of adhering softening bath. No significant removal of softenedgelatin is involved, for example either by brushing or the like or byextended washing to remove softened gelatin.

EXAMPLE 4 OaNu IIzN H O H O The cyan dye image was then transferred by 5seconds contact with a piece of preconditioned commercial (Kodak)transfer paper.

On removal of the imaging medium from the mordanted transfer paper,softened gelatin adhered to the paper, from which it was easily removedby gently swabbing the pring with a wet tissue, without harmful efiectto the transferred dye image therein.

After the making of the first print, the photographic image in theimaging medium was defined therein in relief because of removal of thesoftened gelatin therefrom by transfer to the receptor sheet on makingthe first dye transfer print.

Subsequent dye transfer receptor sheets did not show further significantportions of softened gelatin being transferred from the imaging medium.

What is claimed is:

1. In the method of making dye transfer prints by transferring dye to areceptor surface from a relief image formed from a photographic imagingmedium comprising a supported photosensitive layer of a finely dividedphotoconductor which is reversibly activatable by actinic radiationdispersed in a gelatin binder therefor, said imaging medium bearing aphotographic image defined in said supported layer by portions of saidgelatin binder which have been selectively softened, the improvementwherein dye to be transferred is directly applied to said imaging mediumand then transferred to said receptor surface without prior removal ofsaid selectively softened portions of the gelatin binder, said softenedportions neither significantly taking up nor transferring dye appliedthereto.

2. A process as in claim 1 wherein said supported layer comprises finelydivided titanium dioxide dispersed in a gelatin binder.

3. The method of making a dye transfer print from a direct positivephotographic image which comprises exposing a photosensitive imagingmedium to imaging radiation, said imaging medium comprising a finelydivided photoconductor which is reversibly activatable by actinicradiation dispersed in a gelatin binder therefor; developingradiation-exposed portions of said imaging medium with a developingagent comprising reducible metal ions, whereby free metal is depositedin said radiation-exposed portions; and reoxidizing said free metal tometal ions in the presence of a metal ion-activated softening agent forsaid gelatin binder to soften said binder in radiation-exposed areas toproduce a photographic image of unsoftened gelatin binder; andtransferring dye from said positive photographic image to a receptorsheet without prior removal of softened portions therefrom to therebyform a dye transfer print.

4. The method of making a full color dye transfer positive print whichcomprises respectively exposing three photosensitive imaging media toimaging radiation from a set of red, green, and blue color separationpositives, said imaging media each comprising a finely dividedphotoconductor which is reversibly activatable by actinic radiationdispersed in a supported layer of a gelatin binder therefor, saidphotoconductor being dye sensitized to said imaging radiation;developing radiation-exposed portions of said imaging media with adeveloping agent comprising reducible metal ions, whereby free metal isdeposited in said radiation-exposed portions; reoxidizing said freemetal to metal ions in the presence of a metal ion-activated softeningagent for said gelatin binder to soften said binder in radiation-exposedareas to produce a photographic image of unsoftened gelatin; andsubsequently,

without prior removal of softened portions therefrom, respectivelytaking up cyan, magenta, and yellow dye in unsoftened portions of thebinder of the images respectively prepared by exposure to said red,green, and blue color separation positives; and transferring dye fromsaid images to a receptor sheet in register to produce a full colorpositive dye transfer print.

5. The method of making a full color dye transfer positive print whichcomprises respectively exposing three photosensitive imaging media toimaging radiation from a positive color image through a red, green, andblue filter; said imaging media each comprising a finely dividedphotoconductor which is reversibly activatable by actinic radiationdispersed in a supported layer of a gelatin binder therefor, saidphotoconductor being dye sensitized to said imaging radiation;developing radiation-exposed portions of said imaging media with adeveloping agent comprising reducible metal ions, whereby free metal isdeposited in said radiation-exposed portions; reoxidizing said freemetal to metal ions in the presence of a metal ion-activated sofieningagent for said gelatin binder to soften said binder in radiation-exposedareas to produce a photographic image of unsoftened gelatin; andsubsequently, without prior removal of softened portions therefrom,respectively taking up cyan, magenta and yellow dye in unsoftenedportions of the gelatin binder of the images respectively prepared byexposure through said red, green, and blue filter; and transferring dyefrom said images to a receptor sheet in register to produce a full colorpositive dye transfer print.

6. A method of claim 3 wherein said photoconductor comprises titaniumdioxide.

7. A method of claim 6 wherein said titanium dioxide is dye sensitized.

8. A method of claim 7 wherein said imaging medium comprisingdye-sensitized titanium dioxide is exposed to imaging radiation from apositive color image through a filter passing red, green, or blue lightto which said titanium dioxide is sensitized.

9. A method of claim 7 wherein said imaging medium comprisingdye-sensitized titanium dioxide is exposed through a color separationpositive to imaging radiation to which said titanium dioxide is sensitize d. a 2,

2. A process as in claim 1 wherein said supported layer comprises finelydivided titanium dioxide dispersed in a gelatin binder.
 3. The method ofmaking a dye transfer print from a direct positive photographic imagewhich comprises exposing a photosensitive imaging medium to imagingradiation, said imaging medium comprising a finely dividedphotoconductor which is reversibly activatable by actinic radiationdispersed in a gelatin binder therefor; developing radiation-exposedportions of said imaging medium with a developing agent comprisingreducible metal ions, whereby free metal is deposited in saidradiation-exposed portions; and reoxidizing said free metal to metalions in the presence of a metal ion-activated softening agent for saidgelatin binder to soften said binder in radiation-exposed areas toproduce a photographic image of unsoftened gelatin binder; andtransferring dye from said positive photographic image to a receptorsheet without prior removal of softened portions therefrom to therebyform a dye transfer print.
 4. The method of making a full color dyetransfer positive print which comprises respectively exposing threephotosensitive imaging media to imaging radiation from a set of red,green, and blue color separation positives, said imaging media eachcomprising a finely divided photoconductor which is reversiblyactivatable by actinic radiation dispersed in a supported layer of agelatin binder therefor, said photoconductor being dye sensitized tosaid imaging radiation; developing radiation-exposed portions of saidimaging media with a developing agent comprising reducible metal ions,whereby free metal is deposited in said radiation-exposed portions;reoxidizing said free metal to metal ions in the presence of a metalion-activated softening agent for said gelatin binder to soften saidbinder in radiation-exposed areas to produce a photographic image ofunsoftened gelatin; and subsequently, without prior removal of softenedportions therefrom, respectively taking up cyan, magenta, and yellow dyein unsoftened portions of the binder of the images respectively preparedby exposure to said red, green, and blue color separation positives; andtransferring dye from said images to a receptor sheet in register toproduce a full color positive dye transfer print.
 5. The method ofmaking a full color dye transfer positive print which comprisesrespectively exposing three photosensitive imaging media to imagingradiation from a positive color image through a red, green, and bluefilter; said imaging media each comprising a finely dividedphotoconductor which is reversibly activatable by actinic radiationdispersed in a supported layer of a gelatin binder therefor, saidphotoconductor being dye sensitized to said imaging radiation;developing radiation-exposed portions of said imaging media with adeveloping agent comprising reducible metal ions, whereby free metal isdeposited in said radiation-exposed portions; reoxidizing said freemetal to metal ions in the presence of a metal ion-activated softeningagent for said gelatin binder to soften said binder in radiation-exposedareas to produce a photographic image of unsoftened gelatin; andsubsequently, without prior removal of softened portions therefrom,respectively taking up cyan, magenta and yellow dye in unsoftenedportions of the gelatin binder of the images respectively prepared byexposure through said red, green, and blue filter; and transferring dyefrom said images to a receptor sheet in register to produce a full colorpositive dye transfer print.
 6. A method of claim 3 wherein saidphotoconductor comprises titanium dioxide.
 7. A method of claim 6wherein said titanium dioxide is dye sensitized.
 8. A method of claim 7wherein said imaging medium comprising dye-sensitized titanium dioxideis exposed to imaging radiation from a positive color image through afilter passing red, green, or blue light to which said titanium dioxideis sensitized.
 9. A method of claim 7 wherein said imaging mediumcomprising dye-sensitized titanium dioxide is exposed through a colorseparation positive to imaging radiation to which said titanium dioxideis sensitized.